This invention relates to the art of electrical machines, and more particularly to a new and improved resolver wherein position error due to crosstalk is eliminated.
A basic resolver has a pair of primary windings located at right angles to each other in a rotor and two secondary windings located at right angles to each other in a stator. As the rotor is rotated by a mechanical input, if the rotor winding is excited with a rated input voltage, the output voltage of the one stator winding will be proportional to the cosine of the rotor angle and the output voltage of the other stator winding will be proportional to the sine of the rotor angle.
Thus, the resolver is an analog trigonometric function generator in the form of a rotating transformer which modulates an a.c. excitation signal with the mechanical rotation of the device. The resolver electrical output may be used for position and velocity information. Resolvers are used for moving devices to precise positions with smooth and accurate control, for sensing the position of mechanical devices, for generating speed and position data for robotic, machine tool and aerospace servo applications, and for measuring rotary motion in place of encoders.
In the resolver there is need to transmit the input electrical excitation signal to the rotor windings. Initially this was done using a brush and slip ring sliding contact. Since the brush and slip ring are life-limiting components and can be a source of noise in harsh environments, a brushless resolver was developed wherein a rotary transformer is used to transmit electrical excitation or energy to the rotor.
It has been determined, in accordance with the present invention, that crosstalk between the rotary transformer and the resolver winding in a brushless resolver can give rise to position error in the form of deviation between the indicated electrical position and the actual mechanical position over each revolution of the resolver rotor. It would, therefore, be highly desirable to provide a resolver wherein any deviation between the indicated electrical position of the rotor and the actual mechanical position of the rotor during each resolver revolution is made as small as possible. This must be accomplished by a relatively simple structure which is economical to manufacture.